The invention relates to an electronic component comprising a Josephson junction and to a method for producing the same.
Josephson junctions between high-temperature superconducting (high Tc, HTS) electrodes are a basic building block of superconducting electronics. They are used, among other things, for superconducting quantum interference devices (SQUIDs) for highly sensitive magnetic field measurement and in detectors for THz radiation.
The essential characteristics of a Josephson junction are the critical current density Jc of the superconducting state and the normal-state resistance Rn. These variables, and their Jc*Rn product (or Ic*Rn with the critical current Ic) in particular, are known as quality criteria for the usability of Josephson junctions for the above-mentioned purposes from (E. Mitchell, C. P. Foley, “YBCO step-edge junctions with high JcRn”, Superconductor Science and Technology 23, 065007 (2010). doi:10.1088/0953-2048/23/6/065007). This document discloses that both Jc and Rn at the grain boundary of a YBCO HTS layer are highly dependent on the angle θ between the crystal orientations of the two grains in the YBa2Cu3O7-x (YBCO). It is therefore proposed to grow the layer on a substrate, the surface of which has a step edge. The Josephson junction is created on the upper edge of a slide-shaped step of the substrate surface by introducing a sharp bend having an angle of θ degrees into the crystal structure of YBCO at the edge. A grain boundary forms in the YBCO at the step edge, wherein the angle θ is predefined by the bend angle of the step edge. The bend causes local strain, and consequently a local oxygen deficiency in the YBCO at the grain boundary. The region of the bend therefore acts in the manner of a tunnel contact barrier between two differently oriented d-wave superconductors, and thus forms the weak link of the Josephson junction.
Some of the Josephson junctions produced this way in fact include the high Jc*Rn product hoped for. The drawback is that reproducibility so far is only satisfactory for proof of basic feasibility (proof of concept), not, however, for large-scale production because a high rate of scrap is incurred.
It is therefore the object of the invention to make Josephson junctions made of high-temperature superconductors available which have a high Jc*Rn product and can also be more reproducibly produced than according to the present state of the art.
This object is achieved according to the invention by a component comprising a Josephson junction according to the main claim and by a production method according to the additional independent claim. Further advantageous embodiments will be apparent from the dependent claims referring back to these claims. The invention further relates to a detector for THz radiation and to a SQUID, in which the component according to the invention is used.